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decrepit said..
Tested the helmet mod to take two GPSs along with the V3 logomatic, BN880 logger @ 10hz.
There's still work to be done on the helmet mod, I've held the waterproof pouch in place with the front of an old paqua-midi. Water gets between the two plastic sheets, and probably reduces the satellite signals, although that's hard to pick up in the data.

I had the GW52 and V3 in the helmet, and V2 on my upper right arm.
The three are very close, and these are the ubx missing points

V3
176045 points read: checksum: 0, corrupted: 1, missing: 1
000002: 0019 07 092 This is before any sats have been fixed
004801.102 102ms this is when it goes from 0 sats to 7 sats

V2
86363 points read: checksum: 0, corrupted: 0, missing: 3
005108.400 217ms, this occurs as sats go from 0 to 6
010255.400 201ms, 0.6secs before this is a 0.199
031831.400 201ms, "" "" " " " "

He has a battery to run all the equipment in his backpack. Maybe a flask of tea too.

Thanks Dave, that pic nicely confirms the GPSs are pointing straight up for best sky view. There's only the top of the sail in the way.

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decrepit said..
Thanks Dave, that pic nicely confirms the GPSs are pointing straight up for best sky view. There's only the top of the sail in the way.

And what a lovely looking sail that is!

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sailquik said..

decrepit said..
Thanks Dave, that pic nicely confirms the GPSs are pointing straight up for best sky view. There's only the top of the sail in the way.

And what a lovely looking sail that is!

The photographer likes kit to test , photograph I mean.

I've had several sessions now with the logomatic Bn880 combo using a sandisk extreme card. That seems to have solved the buffer over write problem at 10hz using NAV-PVT + NAV-SAT at 1hz. I'm only getting missed points at initial fix, or where satellite view has substantially changed, and the chip is busy sorting things out, with no time to output data.
But I've run into Peter's problem, the GPSResults's, default acceleration filter setting, of 8m/s2, being too low for 10hz. I think all the 2s results so far are unaffected, but I've had a few 10s and several NMs, where all or part of the run are disallowed, until the acceleration filter is increased, so far going to 12m/s2 is far enough. but Peter thinks it should be double the 5hz setting at 16m/s2.

And the filter setting doesn't seem to relate to the mAcc column in the results, nor to the m/s2 column in the data.

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decrepit said..
And the filter setting doesn't seem to relate to the mAcc column in the results, nor to the m/s2 column in the data.

Hmmmm, thats the bit that worries me.........

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decrepit said..
And the filter setting doesn't seem to relate to the mAcc column in the results, nor to the m/s2 column in the data.

Can you expand on that? I did see the relation to the m/s2 column in the data. Points with numbers above the threshold get filtered.

The numbers in the mAcc column should alway be below the threshold if filters are on.

BTW, your tip to change settings with a small file before loading a big file does not seem to work. When opening a new file, GPSResults uses the default settings for the new file. That's a genuine PITA with the Mac version, since GPSResults also re-calculates things after every little change of the filter settings.

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decrepit said..
I've had several sessions now with the logomatic Bn880 combo using a sandisk extreme card. That seems to have solved the buffer over write problem at 10hz using NAV-PVT + NAV-SAT at 1hz. I'm only getting missed points at initial fix, or where satellite view has substantially changed, and the chip is busy sorting things out, with no time to output data.
But I've run into Peter's problem, the GPSResults's, default acceleration filter setting, of 8m/s2, being too low for 10hz. I think all the 2s results so far are unaffected, but I've had a few 10s and several NMs, where all or part of the run are disallowed, until the acceleration filter is increased, so far going to 12m/s2 is far enough. but Peter thinks it should be double the 5hz setting at 16m/s2.

And the filter setting doesn't seem to relate to the mAcc column in the results, nor to the m/s2 column in the data.

The point of an acceleration-filter, is to say "this point looks suspicious" *and* "the acceleration looks suspicious".... at 1Hz, those both align to mean the same thing.

But at 10Hz they aren't aligned - there should be two filters, a) measuring the acceleration-per-second and b) the adjacent-point-acceleration.

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mathew said.. >>>> But at 10Hz they aren't aligned - there should be two filters, a) measuring the acceleration-per-second and b) the adjacent-point-acceleration.

That sounds right, but is there?

So m/s2 set to 8.5, the largest number in the m/s2 data column I could find is 5.2, the results field says mAcc10.5.
And with the filter set at 8/ms2 this result doesn't appear. It's all very confusing.

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mathew said..
But at 10Hz they aren't aligned - there should be two filters, a) measuring the acceleration-per-second and b) the adjacent-point-acceleration.

I agree that the acceleration in 10 Hz data needs to be calculated over longer periods, not just adjacent points. One second should work much better.

The "adjacent point-acceleration" is what's currently implemented. But single points sometimes have random errors of +- 0.5 m/s (1 knot). If two neighboring points happen to go in opposite directions, the difference is 1 m/s, within 0.1 seconds. That gives an acceleration of 10 m/s2, which is above the default filter setting ( 8 m/s2 for data of 5 and 10 Hz). If the points are in the middle of a run, GPSResults will not score the run.

In the example above, simply using the average acceleration over two points for filter purposes would fix the problem.

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boardsurfr said..
>>>BTW, your tip to change settings with a small file before loading a big file does not seem to work. When opening a new file, GPSResults uses the default settings for the new file. That's a genuine PITA with the Mac version, since GPSResults also re-calculates things after every little change of the filter settings.

Yes sorry about that!
It does work for min speed, I've done that a lot, but I guess the acceleration filter, needs to know, what frequency the file is at. So it has to be set for every file.

V3 logomatic had a rare intermittent, I had a couple of sessions with 2 or 3 files, with only a few ms between them. So the other day I had a go at finding and fixing the problem. The problem points were at bad "offs" so I tried pressing various points on the boards, and managed to reproduce the problem. Trouble was I went on pressing try to find the exact location, at some stage I heard a light "crack", now of course the fault is 10X worse, the recording function stops and starts with the smallest of shakes.

Can I fix this????
Who knows, it'll probably just sit on this desk alongside sluggers watch, waiting for inspiration.
Trouble is this thing is expensive, $90, and power hungry, maybe if I really want a 10hz unit I'll wait for the motion to come on line.

Great result! Problem was the plug into the bn880, the socket had a small bit of stuff inside it, stopping it from seating properly.
Now I've fixed that, it's been working fine.
I've been seeing how high I can push it with NAV-SAT deselected. I still had a few missed points at 14hz, but 12.5 is doing much better, only 1 missed in 6hrs.

Next thing to in my spare time is see what difference frequency makes to accuracy.